A015948 a(n) = smallest k >= n such that k | (2^k + n).

1, 2, 5, 4, 7, 10, 15, 8, 11, 14, 13, 28, 21, 78, 17, 16, 19, 22, 49, 42, 23, 26, 1577, 40, 33, 30, 29, 44, 31, 34, 39, 32, 65, 38, 37, 52, 115, 102, 41, 242, 43, 46, 51, 60, 47, 279, 395, 152, 57, 114, 53, 68, 85, 58, 63, 104, 59, 62, 61, 76, 69, 126, 5773, 64, 67, 1090

Offset: 0

Author

Robert G. Wilson v

Keywords

• nonn

Comments

Equally, a(n) = smallest k with 2^k mod k = k - n.

Crossrefs

Cf. A015910, A036236.

Formula

a(p-2) = p for p prime >= 5; a(2^k) = 2^k. - David W. Wilson

Extensions

Edited by N. J. A. Sloane, Jan 31 2009 at the suggestion of R. J. Mathar and T. D. Noe.

Restricted the range of k in the definition - R. J. Mathar, Mar 07 2010